1. Field of the Invention
The present invention relates generally to wheel rakes. More particularly, the present invention relates to an improved suspension system for rakes having one or more floating rake wheels wherein the suspension hydraulic cylinders are also used to lift for transport.
2. Background Art
Some prior art wheel rakes use coil springs in tension to apply a lift force onto each rake wheel in an attempt to get each rake wheel to “float”. The term ground force in this specification is intended to describe the force equal to the lift force subtracted from the weight of the individual rake wheel. If the lift force is equal to the weight of the rake wheel the ground force will be equal to zero. If the lift force exceeds the weight of the rake wheel, as can occur in a dynamic condition, the ground force will be negative, causing the rake wheel to be accelerating upward. If the lift force is zero, then the ground force is equal to the weight of the rake wheel. The prior art arrangement results in the situation that as each rake wheel is lifted up the ground force changes dramatically, because its respective spring is quite linear in force as it is stretched. It is common for the ground force to vary from zero, to the full weight of the rake wheel within 6 to 8 inches of travel. This application of uneven force of each rake wheel against the ground is, of course, undesirable.
Prior art wheel rakes also used a system of push tubes or push or pull tubes to move the rake wheels from an operating position to a transport position. Those systems were always notoriously prone to bending, flexing and often were the cause of breakdowns, which also is a problem.
Another problem relating to large wide rakes is that they do not have flex joints in them. Thus, when the wheels passed over a low spot, in areas where there is irregular terrain, these large rakes will still miss picking up the crop because one or more of the rake wheels will not go low enough in a dip in the field.
In prior art rakes that use a chain to limit up and down limits of each individual rake wheel, each individual one of the chain links on the machine needs to be adjusted separately at the beginning of the raking process and if during use it appears that the adjustments were not optimum, then each one needs to be adjusted again in a fine tuning process. This process may need to be repeated at other times too, when conditions change.
Another problem with the prior art system of using chains to limit the up and down movement of each individual rake wheel is that the parts are loose causing rattling noises during transport from place to place and to some extent even during use in the raking process.
There is, therefore, a need for providing an improved suspension system for rake wheel rakes on a raking implement.